From: "Arnd Bergmann" <arnd@arndb.de>
To: "Peter Zijlstra" <peterz@infradead.org>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Will Deacon" <will@kernel.org>,
"Boqun Feng" <boqun.feng@gmail.com>,
"Mark Rutland" <mark.rutland@arm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
dennis@kernel.org, "Tejun Heo" <tj@kernel.org>,
"Christoph Lameter" <cl@linux.com>,
"Heiko Carstens" <hca@linux.ibm.com>,
gor@linux.ibm.com, "Alexander Gordeev" <agordeev@linux.ibm.com>,
borntraeger@linux.ibm.com, "Sven Schnelle" <svens@linux.ibm.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Joerg Roedel" <joro@8bytes.org>,
suravee.suthikulpanit@amd.com,
"Robin Murphy" <robin.murphy@arm.com>,
dwmw2@infradead.org, "Baolu Lu" <baolu.lu@linux.intel.com>,
"Herbert Xu" <herbert@gondor.apana.org.au>,
"David S . Miller" <davem@davemloft.net>,
"Pekka Enberg" <penberg@kernel.org>,
"David Rientjes" <rientjes@google.com>,
"Joonsoo Kim" <iamjoonsoo.kim@lge.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Roman Gushchin" <roman.gushchin@linux.dev>,
"Hyeonggon Yoo" <42.hyeyoo@gmail.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-s390@vger.kernel.org,
iommu@lists.linux.dev, Linux-Arch <linux-arch@vger.kernel.org>,
linux-crypto@vger.kernel.org
Subject: Re: [PATCH v2 05/10] percpu: Wire up cmpxchg128
Date: Mon, 06 Feb 2023 14:20:06 +0100 [thread overview]
Message-ID: <86c8ba70-2a2f-4c5b-8e74-20e3823e2db3@app.fastmail.com> (raw)
In-Reply-To: <Y+D3F2pg7X4XFT4r@hirez.programming.kicks-ass.net>
On Mon, Feb 6, 2023, at 13:48, Peter Zijlstra wrote:
> On Mon, Feb 06, 2023 at 01:14:28PM +0100, Peter Zijlstra wrote:
>> On Mon, Feb 06, 2023 at 12:24:00PM +0100, Peter Zijlstra wrote:
>> Basically, using 64bit percpu ops on 32bit is already somewhat dangerous
>> -- wiring up native cmpxchg64 support in that case seemed an
>> improvement.
>>
>> Anyway... let me get on with doing explicit
>> {raw,this}_cpu_cmpxchg{64,128}() thingies.
>
> I only converted x86 and didn't do the automagic downgrade...
>
> Opinions?
I think that's much better, it keeps the interface symmetric
between cmpxchg and this_cpu_cmp_cmpxchg, and makes it harder
to run into the subtle corner case on old x86 CPUs.
For the M486/M586/MK8/MPSC/MATOM/MCORE2 configs, I would
probably want to go with a compile-time check and have most
distro kernels build with at least M586TSC for 32-bit or
an upgraded CONFIG_GENERIC_CPU for x86_64 that assumes cmpxchg16b
(nehalem, second-geneneration k8, silverthorne, ...) in
order to turn system_has_cmpxchg* into a constant value on
all architectures. That can be a separate discussion though
and shouldn't block your series as you just keep the current
state.
> -#ifdef system_has_freelist_aba
> +#ifdef syste_has_freelist_aba
Typo
Arnd
next prev parent reply other threads:[~2023-02-06 13:20 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-02 14:50 [PATCH v2 00/10] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() Peter Zijlstra
2023-02-02 14:50 ` [PATCH v2 01/10] cyrpto/b128ops: Remove struct u128 Peter Zijlstra
2023-02-02 20:21 ` H. Peter Anvin
2023-02-02 14:50 ` [PATCH v2 02/10] types: Introduce [us]128 Peter Zijlstra
2023-02-02 14:50 ` [PATCH v2 03/10] arch: Introduce arch_{,try_}_cmpxchg128{,_local}() Peter Zijlstra
2023-02-02 17:04 ` Heiko Carstens
2023-02-03 16:52 ` Mark Rutland
2023-02-02 14:50 ` [PATCH v2 04/10] instrumentation: Wire up cmpxchg128() Peter Zijlstra
2023-02-03 16:55 ` Mark Rutland
2023-02-02 14:50 ` [PATCH v2 05/10] percpu: Wire up cmpxchg128 Peter Zijlstra
2023-02-02 17:05 ` Heiko Carstens
2023-02-03 17:02 ` Mark Rutland
2023-02-03 17:25 ` Arnd Bergmann
2023-02-06 11:24 ` Peter Zijlstra
2023-02-06 12:14 ` Peter Zijlstra
2023-02-06 12:48 ` Peter Zijlstra
2023-02-06 13:20 ` Arnd Bergmann [this message]
2023-02-06 12:19 ` Arnd Bergmann
2023-02-02 14:50 ` [PATCH v2 06/10] x86,amd_iommu: Replace cmpxchg_double() Peter Zijlstra
2023-02-02 14:50 ` [PATCH v2 07/10] x86,intel_iommu: " Peter Zijlstra
2023-02-03 2:51 ` Baolu Lu
2023-02-02 14:50 ` [PATCH v2 08/10] slub: " Peter Zijlstra
2023-02-08 13:31 ` Hyeonggon Yoo
2023-02-02 14:50 ` [PATCH v2 09/10] arch: Remove cmpxchg_double Peter Zijlstra
2023-02-08 13:44 ` Hyeonggon Yoo
2023-02-02 14:50 ` [PATCH v2 10/10] s390/cpum_sf: Convert to cmpxchg128() Peter Zijlstra
2023-02-02 17:05 ` Heiko Carstens
2023-02-02 19:39 ` [PATCH v2 00/10] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() Linus Torvalds
2023-02-02 22:45 ` David Laight
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